linux-kernel - Re: [PATCH 1/3 v4] resources: introduce generic page_is

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Message-Id: <20100126163058.1f2f6582.akpm@linux-foundation.org>
Date:	Tue, 26 Jan 2010 16:30:58 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Chen Liqin <liqin.chen@...plusct.com>,
	Lennox Wu <lennox.wu@...il.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Américo Wang <xiyou.wangcong@...il.com>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Zheng, Shaohui" <shaohui.zheng@...el.com>
Subject: Re: [PATCH 1/3 v4] resources: introduce generic page_is_ram()

On Fri, 22 Jan 2010 16:16:19 +0800
Wu Fengguang <fengguang.wu@...el.com> wrote:

> 
> It's based on walk_system_ram_range(), for archs that don't have
> their own page_is_ram().
> 
> The static verions in MIPS and SCORE are also made global.
> 
> v4: prefer plain 1 instead of PAGE_IS_RAM (H. Peter Anvin)
> v3: add comment (KAMEZAWA Hiroyuki)
>     "AFAIK, this "System RAM" information has been used for kdump to
>     grab valid memory area and seems good for the kernel itself."
> v2: add PAGE_IS_RAM macro (Am__rico Wang)
> 
> CC: Chen Liqin <liqin.chen@...plusct.com>
> CC: Lennox Wu <lennox.wu@...il.com>
> CC: Ralf Baechle <ralf@...ux-mips.org>
> CC: Am__rico Wang <xiyou.wangcong@...il.com>
> CC: linux-mips@...ux-mips.org
> CC: Yinghai Lu <yinghai@...nel.org>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> 
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> ---
>  arch/mips/mm/init.c    |    2 +-
>  arch/score/mm/init.c   |    2 +-
>  include/linux/ioport.h |    2 ++
>  kernel/resource.c      |   13 +++++++++++++
>  4 files changed, 17 insertions(+), 2 deletions(-)
> 
> --- linux-mm.orig/kernel/resource.c	2010-01-22 11:20:34.000000000 +0800
> +++ linux-mm/kernel/resource.c	2010-01-22 16:12:55.000000000 +0800
> @@ -327,6 +327,19 @@ int walk_system_ram_range(unsigned long 
>  
>  #endif
>  
> +static int __is_ram(unsigned long pfn, unsigned long nr_pages, void *arg)
> +{
> +	return 1;
> +}
> +/*
> + * This generic page_is_ram() returns true if specified address is
> + * registered as "System RAM" in iomem_resource list.
> + */
> +int __attribute__((weak)) page_is_ram(unsigned long pfn)
> +{
> +	return walk_system_ram_range(pfn, 1, NULL, __is_ram) == 1;
> +}

I'll switch this to use __weak.

>  /*
>   * Find empty slot in the resource tree given range and alignment.
>   */
> --- linux-mm.orig/include/linux/ioport.h	2010-01-22 11:20:34.000000000 +0800
> +++ linux-mm/include/linux/ioport.h	2010-01-22 11:20:35.000000000 +0800
> @@ -191,5 +191,7 @@ extern int
>  walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
>  		void *arg, int (*func)(unsigned long, unsigned long, void *));
>  
> +extern int page_is_ram(unsigned long pfn);

Is it appropriate that this function be declared in ioport.h?  It's a
pretty general function.  Dunno.

>  #endif /* __ASSEMBLY__ */
>  #endif	/* _LINUX_IOPORT_H */
> --- linux-mm.orig/arch/score/mm/init.c	2010-01-22 11:20:34.000000000 +0800
> +++ linux-mm/arch/score/mm/init.c	2010-01-22 11:20:35.000000000 +0800
> @@ -59,7 +59,7 @@ static unsigned long setup_zero_page(voi
>  }
>  
>  #ifndef CONFIG_NEED_MULTIPLE_NODES
> -static int __init page_is_ram(unsigned long pagenr)
> +int page_is_ram(unsigned long pagenr)
>  {
>  	if (pagenr >= min_low_pfn && pagenr < max_low_pfn)
>  		return 1;
> --- linux-mm.orig/arch/mips/mm/init.c	2010-01-22 11:20:34.000000000 +0800
> +++ linux-mm/arch/mips/mm/init.c	2010-01-22 11:20:35.000000000 +0800
> @@ -298,7 +298,7 @@ void __init fixrange_init(unsigned long 
>  }
>  
>  #ifndef CONFIG_NEED_MULTIPLE_NODES
> -static int __init page_is_ram(unsigned long pagenr)
> +int page_is_ram(unsigned long pagenr)
>  {
>  	int i;

hm, so we lose the __init.

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